Better by Design

The new C8 and the C8.R racecar were engineered side-by-side, resulting in the fastest, most efficient Corvettes ever

Photo: Better by Design 1
February 6, 2020

The introduction of the C8.R racecar opens the next chapter in Corvette’s illustrious motorsports history. Building on a 20-plus-year legacy of success around the globe, the team of experts responsible for Corvette Racing has crafted a beautiful, new car that’s a complete departure from all that came before—and yet is the closest to its production counterpart of any Corvette racer thus far. This symbiosis between the road and racing versions goes back to the fact that they were developed simultaneously, which did not happen with prior-generation Corvettes.

“Historically, there is a serial relationship,” explains Corvette chief engineer Ed Piatek. “We had the C5 on the road in 1997, and started to develop that racecar for the 1999 season. Many things we learned there were part of the tech transfer that went into C5, then C6 into C6.R, and so on. But in this case, we [had] a clean sheet of paper for both cars, and had a chance to design and develop them together for the first time ever. As a result, there is a deeper level of technology transfer between the 2020 Corvette Stingray and the next-generation Corvette racecar than ever before.”

The closer-than-ever relationship between the race and production cars was made possible by more extensive use of extremely advanced computer analytics than ever before. These tools empowered the engineers to start the design of the C8.R well in advance of any production C8 components being available. Chevrolet’s state-of-the-art Driver in the Loop simulator was heavily utilized to evaluate numerous chassis and aero design concepts before a single part was produced. When an idea looked promising, the engineering and design teams were able to quickly make thousands of 3D-printed rapid prototype parts for chassis and wind-tunnel testing.

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A heavily camouflaged C8.R undergoes wind-tunnel testing in Michigan early last year. Finding the right balance of aerodynamic efficiency, downforce, and cooling was a challenge.

All told, the race and road cars share 80 different parts. Chief among them is the chassis structure, made in the Bowling Green Assembly Plant with a very sophisticated combination of riveted- and bonded-aluminum components. This frame is both lighter and stiffer than that of any previous Corvette. That stiffness is further increased in the C8.R with the addition of a full safety cage.

While the two cars share the same basic short-/long-arm double-wishbone suspension and suspension pickup points, they don’t use the same components. The C8 relies on forged aluminum upper and cast aluminum lower arms, while the racecar uses fabricated steel arms all around. And in accord with the rules governing IMSA racing, the C8.R also has different shock absorbers and brakes. Its shocks are adjustable coil-overs, while its brake system includes Alcon monobloc six-piston front and four-piston rear calipers. These squeeze steel rotors that are a little bit larger than the stock units.

As with previous-generation racecars, the C8.R’s body is a slightly wider and lower version of its street counterpart, made entirely with lightweight carbon fiber. The car measures 80.7 inches wide and 45.1 inches high, versus the street car at 76.1 and 48.6 inches, respectively. Both bodies are 182.3 inches long, but the racecar is slightly longer overall if you consider the rear wing and splitter overhang.

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Next, the car was evaluated on various racetracks, where its suspension, engine computer, and other aspects were calibrated and refined.

More so than ever, aerodynamic efficiency drove the design of the C8 and C8.R bodies, and the new mid-engine architecture allowed for significant improvements in this area compared with earlier Corvettes. This was particularly true for the racecar because the C7.R was not able to take full advantage of a 2016 rule change that allowed for larger front splitters and rear diffusers. At the time, it wasn’t feasible to make the substantial changes to the chassis and suspension that would have been required to free up room for the bigger aero parts.

In creating the new car, engineers were able to incorporate the larger splitter and diffuser into their plan from day one, in effect designing the adjacent structures around them. Finding space for the front diffuser was relatively easy given that the engine is not in the way, but the rear was quite a bit more complex. One big help was a new, more compact sequential six-speed gearbox designed specifically for the C8.R by Corvette Racing technical partner Xtrac.

On the body’s top surfaces, most of the basic aero goals were the same for the race and street cars. Both needed to slip through the air with minimal drag to reduce fuel consumption, and both needed balanced downforce between the front and rear. That said, it’s safe to say that fuel economy was a bit more important for the 2020 Stingray, while downforce was more critical for the C8.R.

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Another aspect of handling airflow over, under, and through the body, and one that was especially challenging for the racecar, pertains to thermal management. With previous Corvette racers, the two biggest generators of heat—the engine and gearbox—were at opposite ends of the car, so their thermal loads could be managed separately. In the C8.R, with the engine and gearbox together, it’s more difficult to keep them—as well as all of the parts attached to and surrounding them, such as alternators, compressors, starters, and electronics—sufficiently cool. To help address this, designers placed the engine’s air intake at the base of the rear window. While this has a slightly adverse impact on airflow to the rear wing, it does free up the large air intakes on either side of the car, which are used for engine intake air on the street car, to help with cooling. Also helping manage heat load at the rear is the placement of the engine’s radiator up front, in the center area allocated for storage in the street car. After air passes through the radiator, it exits by way of ducts behind each front wheel.

In keeping with IMSA rules, the C8.R’s engine displaces 5.5 liters. While this is the same as the C7.R’s engine, the two powerplants share almost nothing in common. The new engine, which is a radical departure from anything seen in a Corvette racecar previously, is a naturally aspirated, dual-overhead-camshaft, four-valve-per-cylinder V-8 with a flat-plane crankshaft. The four-valve cylinder heads breathe better, and the absence of counter-weighting on the flat-plane crank makes the engine much more responsive.

The C8.R’s clean-sheet design and mid-engine architecture have yielded a lighter, stiffer vehicle with better aerodynamics, improved weight distribution, quicker reflexes, and a host of other enhancements. Combined, these will go a long way in ensuring that the newest-generation Corvette racecars continue the winning legacy of their predecessors.

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Corvette Racing’s Gavin, Garcia, and Milner provide input.

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Also from Issue 136

  • ProCharged ’88 Convertible
  • 522-CI ’70 Custom
  • $20K Market Report
  • Restored ’67 L89
  • Small-Block ’53 Tribute
  • History: Mid-Engine Corvette Prototypes
  • Interview: Kai Spande
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